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    Wyświetlanie 1-9 z 9
    Tytuł:
    Determination of sound power level by using a microphone array and conventional methods
    Autorzy:
    Bogusławski, Grzegorz
    Kopania, Joanna Maria
    Gaj, Patryk
    Wójciak, Kamil
    Powiązania:
    https://bibliotekanauki.pl/articles/127805.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    sound power level
    ISO methods
    microphone array
    intensity probe
    poziom mocy akustycznej
    metody ISO
    macierz mikrofonów
    sonda natężeniowa
    Opis:
    Sound power is measured to make objective comparisons between the same type of products, but also because legislation requires it. To release a new product, it is often compulsory to certify it according to International Organization for Standardization (ISO) standards, and also with national and local regulations. Determining of sound power is not a straightforward process. Sound power can be determined through the measurement of sound pressure (series 3740 methods) or sound intensity (series 9614 methods). Selecting one of the above methods depends on the purpose of the test, as well as the available equipment, desired grade of accuracy, background noise level or the test environment. Nowadays the additional methods, such as microphone arrays are used to located of the noise source and determined of pressure sound level. But the results obtained with acoustic cameras cannot be, for now, used for legislative purposes (are not ISO compliant). In this work the differences in the determination of sound power level by using conventional ISO methods and microphone arrays are determined. The system composed of a loudspeaker and a fan were used as a sound source of the noise. Sound power levels according to ISO 3746 and ISO 9614-1 were determined and were compared with the developed method by using microphone arrays techniques.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-8
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessment of sound absorbing properties of composite made of recycling materials
    Autorzy:
    Gaj, Patryk
    Kopania, Joanna
    Wójciak, Kamil
    Bogusławski, Grzegorz
    Powiązania:
    https://bibliotekanauki.pl/articles/128049.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    sound absorbing materials
    recycling
    sound absorption coefficient
    composite materials
    materiały dźwiękochłonne
    recykling
    współczynnik pochłaniania dźwięku
    materiały kompozytowe
    Opis:
    In modern world we are searching methods to reuse most of industrial disposals produced during manufacturing. Some kinds of materials, like scraps from acoustic foam, however are not so easily utilized using recycling methods for its primary usage. Disposals produced during the manufacturing process can be compressed and reused as sound absorbing material. The purpose of this article is to examine sound absorbing properties of material made of acoustic foam disposals and compare it with sound protection materials, which are commonly used. Sound absorbing damping were tested using Kundt’s tube and reverberation room examination method. Tests were carried out according to standard PN-EN ISO 354:2005, for reverberation room examination, and according to Bruel&Kjaer electronic instruments technical manual for Kundt’s tube examination.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-7
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of shell shape on flow and acoustic parameters of a steam silencer
    Autorzy:
    Gaj, Patryk
    Sobczak, Krzysztof
    Kopania, Joanna
    Wójciak, Kamil
    Powiązania:
    https://bibliotekanauki.pl/articles/1955072.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    acoustics
    CFD
    noise emission
    steam silencer
    Opis:
    Steam discharge produces noise due to rapid expansion and a temperature drop of ejected steam. This is why steam silencers are used to change one-stage into multi-stage expansion, which reduces the intensity of pressure and temperature drop during this process and shifts emitted noise into higher frequencies, which are easier to dampen. This paper presents a flow-acoustic numerical model of a steam silencer. It is meant to help to obtain a precise analysis of phenomena occurring in steam silencers and improve the process of designing this type of device. The model described in this paper was based on the parameters of a real working unit manufactured in the Institute of Power Engineering – Thermal Technology Branch. Most of the steam silencers are designed based on construction guidelines that have not been changed for a long time. This restrained an increase in the acoustics efficiency of the steam silencers. An improvement of their flow and acoustic properties allows for the development of smaller, more efficient, and lighter construction. The current version of the model was used for the analysis of flow and acoustic changes which occur after modifying the lower region of a shell of the steam silencer. The proposed modification allowed for a 19% increase in mass flow rate through the silencer and noise reduction in the low-frequency range.
    Źródło:
    Archives of Thermodynamics; 2021, 42, 4; 141-154
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Przenośne ekrany akustyczne
    Autorzy:
    Kazimierska-Grębosz, Marianna
    Grądzki, Ryszard
    Niezgodziński, Tadeusz
    Kopania, Joanna
    Powiązania:
    https://bibliotekanauki.pl/books/2020071.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Łódzka. Wydawnictwo Politechniki Łódzkiej
    Opis:
    Hałas występujący w środowisku, nazywany hałasem środowiskowym lub hałasem zewnętrznym, dotyczy środowiska znajdującego się poza miejscem pracy, na zewnątrz budynków mieszkalnych. Hałas ten oddziałuje na wszystkich obywateli, jest zagrożeniem występującym we wszystkich elementach środowiska. W środowisku miejskim o poziomie hałasu decyduje w głównej mierze hałas komunikacyjny. Hałas komunikacyjny to hałas emitowany przez środki transportu, komunikacji drogowej, komunikacji kolejowej, komunikacji lotniczej i wodnej. Poziom hałasu komunikacyjnego jest zróżnicowany, obejmuje największą grupę ludności i dlatego jest obiektem szczególnej uwagi. Poziom hałasu komunikacyjnego w środowisku miejskim znacząco wzrasta, gdy na ulicach miast prowadzone są prace drogowe, które wykonywane są często bez wyłączenia ruchu. Wstępne pomiary hałasu, przeprowadzone w obrębie prac remontowych ulic oraz w budynkach przy arteriach komunikacyjnych na wybranym terenie miejskim, wskazują na przekroczenia dopuszczalnych wartości poziomu hałasu.
    Noise related to the road works, despite the short-term and local character, disrupts the condition of the acoustic environment. It is necessary to use all possible methods of protection against noise arising during repairs of roads and streets, which are carried out over a long period of time. One of the methods is the application of portable acoustic screens that reduce noise immission into the environment. The possibility of the screens application was analysed in this study. The Authors examined the level of noise in the environment in which the small earthmoving machines were working. The noise levels measured during the operation of different machines were referred to the existing regulations. It was found that the allowed levels of environmental noise during operation of all tested machines have been exceeded from 4 dB to 42 dB. Five models of acoustic screens and two models of acoustic curtain were designed, produced and tested. The dimensions of models where adapted to the size of machines. The ability of easily displacement of models – while the machine is running – was also taken into account. Measurements of sound insulation - Insertion Loss (IL) were determined. IL represents the effectiveness of the application of acoustic screen. Reduction of the noise level for tested machines was confirmed while application of all models of acoustic screens. Value of IL varied for different screens, as well as for different frequencies of emitted sound. All tested screens presented the lowest efficacy for the frequency 125-250 Hz (IL was 2-6 dB). For the frequencies 1000-8000 Hz, effective insulation of screens reached even 15-19 dB. In this monography, the important experimental study concerning the impact of various factors on the isolation of models screens, was presented.
    Dostawca treści:
    Biblioteka Nauki
    Książka
    Tytuł:
    Aeroacoustical study of the serrated ventilation dampers
    Autorzy:
    Kopania, Joanna Maria
    Bogusławski, Grzegorz
    Wójciak, Kamil
    Gaj, Patryk
    Powiązania:
    https://bibliotekanauki.pl/articles/24201973.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    aeroacoustics
    ventilation
    plane damper
    serrated edge
    aeroakustyka
    wentylacja
    przepustnica jednopłaszczyznowa
    krawędź ząbkowana
    Opis:
    The serrated ventilation dampers for regulation of airflow volume were tested. The computer fluid flow analysis was conducted using the Comsol program. The nature of the flow through the serrated ventilation damper was analyzed to identify the different turbulence regions formed on the airflow field. Additionally, the aerodynamical and acoustical parameters of these blades of ventilation dampers with different serrated trailing and/or leading-edge were studied. The aeroacoustic studies were done in the reverberation room. The sound power level and loss coefficient were determined for the studied models.
    Źródło:
    Vibrations in Physical Systems; 2022, 33, 3; art. no. 2022313
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Noise emission from various shape rods at low-moderate Reynolds number
    Autorzy:
    Kopania, Joanna Maria
    Bogusławski, Grzegorz
    Powiązania:
    https://bibliotekanauki.pl/articles/2146658.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    noise
    circular square rods
    u-shape beam
    sound pressure level
    hałas
    pręt kołowy
    pręt kwadratowy
    belka w kształcie litery U
    poziom ciśnienia akustycznego
    Opis:
    Aeroacoustic source localization is an important experimental tool and the first step to know the mechanism of noise generation. The flow around the various shape of rods is one of the major aeroacoustic noise source mechanism. Such rods represent simple models for technical applications like part of the landing gear of planes, train pantographs, antennas, vehicles part, ventilation system or bridge. The purpose of this paper is to clarify the influence of the rod shape in the noise generation mechanism in a low-moderate Reynolds number. In this work, the situation when various shape rods are in the area of laminar-turbulent flow was analyzed. The measurements were carried out for single circular, square, c-shape rods to study the noise effect depended on the Reynolds number. The measurements were performed on the specially constructed test stand with the outlet to the anechoic room. The 1/3 SPL differential spectrum as 2-D noise maps were obtained for studied rods. The acoustic differences between circular, square and U-beam rods were observed.
    Źródło:
    Vibrations in Physical Systems; 2021, 32, 2; art. no. 2021202
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Noise radiation from circular rods at low-moderate Reynolds number
    Autorzy:
    Kopania, Joanna Maria
    Bogusławski, Grzegorz
    Gaj, Patryk
    Wójciak, Kamil
    Powiązania:
    https://bibliotekanauki.pl/articles/128113.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    aeroacoustic noise
    circular rod
    low Reynolds number
    hałas aeroakustyczny
    pręt kołowy
    niska liczba Reynoldsa
    Opis:
    The well-known dominant sources of airframe noise are associated with unsteadiness of separated and/or vortical flow regions around the high-lift system (flaps, slats) and the aircraft undercarriage (landing gear). Current practical landing gear noise prediction models are individual component - based, which means that the various components are divided into groups according to the frequency range, in which they predominantly radiate noise. Since the far-field noise spectra are approximately Strouhal - based, the emitted frequency is assumed to be directly related to their size: the large elements are responsible for the low frequency region of the spectra, and the small components for the high frequency region. On the basis of such understanding of the noise generation mechanism, the special configurations that lead to considerable noise suppression were proposed. One element of these configurations are rods with different shape and cross section. In this work the situation when circular rods are in area of laminar-turbulent flow were analysed. The measurements were carried out for single circular rod with different diameters to study the noise effect depended on Reynolds number. Far field noise for broad range of Reynolds numbers was also examined depending on distance from the source of noise.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-8
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Correlation between the shape of substitution ducts and insertion loss of silencers
    Autorzy:
    Wójciak, Kamil
    Kopania, Joanna Maria
    Powiązania:
    https://bibliotekanauki.pl/articles/2202426.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    silencer
    insertion loss
    aeroacoustics
    tłumik
    strata wtrąceniowa
    aeroakustyka
    Opis:
    Silencers are typical devices used for the reduction of noise in ventilation systems, which can be found in almost all industrial, service or residential installations. Determination of acoustic parameters for specific HVAC devices, like silencers, is within the scope of specialised laboratories. With the silencers, two main parameters should be taken care of: the first one is sound attenuation and the second one is pressure losses. In the presented paper, the focus is on measurement methods described by standard ISO 7235:2009. This standard specifies the methods for determining the sound power level of the flow noise generated by silencers, the total pressure of silencers and the insertion loss of silencers with and without airflow by using the substitute object. In this work, we focused on the correlation between the shape of the substitution duct and its acoustic parameters and its relation to this with the final result of insertion loss of a silencer.
    Źródło:
    Vibrations in Physical Systems; 2022, 33, 2; art. no. 2022212
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The impact of the damper blade position on the generated noise and pressure losses in plenum box with swirl diffusers
    Autorzy:
    Wójciak, Kamil
    Gaj, Patryk
    Kopania, Joanna
    Bogusławski, Grzegorz
    Powiązania:
    https://bibliotekanauki.pl/articles/127800.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    HVAC
    noise emission
    sound power level
    pressure loss
    optimization
    emisja hałasu
    poziom mocy akustycznej
    strata ciśnienia
    optymalizacja
    Opis:
    The article presents the effect of setting the throttle in the plenum box with swirl diffuser on the generated noise and the pressure losses. The sound power levels of the source was determined using the precision method in the reverberation room in accordance with the PN-EN ISO 3741:2011 standard. The examination was carried out for damper blade position set vertically and horizontally for full opening and at a 45 degree angle in both directions. In order to confirm the universality of the conducted experiment, the tests were carried out for two different face swirl diffuser with different shapes of air control blades and holes in the plate and for different flow rates. The multi-criteria optimization methods were used to select the best throttle position.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-8
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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